Transfer of Intracellular HIV Nef to Endothelium Causes Endothelial Dysfunction

Abstract

With effective antiretroviral therapy (ART), cardiovascular diseases (CVD) are emerging as a major cause of morbidity and death in the aging HIV-infected population. To address whether HIV-Nef, a viral protein produced in infected cells even when virus production is halted by ART, can lead to endothelial activation and dysfunction, we tested Nef protein transfer to and activity in endothelial cells. We demonstrated that Nef is essential for major endothelial cell activating effects of HIV-infected Jurkat cells when in direct contact with the endothelium. In addition, we found that Nef protein in endothelial cells is sufficient to cause apoptosis, ROS generation and release of monocyte attractant protein-1 (MCP-1). The Nef protein-dependent endothelial activating effects can be best explained by our observation that Nef protein rapidly transfers from either HIV-infected or Nef-transfected Jurkat cells to endothelial cells between these two cell types. These results are of in vivo relevance as we demonstrated that Nef protein induces GFP transfer from T cells to endothelium in CD4.Nef.GFP transgenic mice and Nef is present in chimeric SIV-infected macaques. Analyzing the signal transduction effects of Nef in endothelial cells, we found that Nef-induced apoptosis is mediated through ROS-dependent mechanisms, while MCP-1 production is NF-kB dependent. Together, these data indicate that inhibition of Nef-associated pathways may be promising new therapeutic targets for reducing the risk for cardiovascular disease in the HIV-infected population.

Increased cardiovascular disease risk in the HIV-positive population on ART: potential role of HIV-Nef and Tat

“…Our and other groups [66, 68] have demonstrated Nef protein in endothelium of coronary and pulmonary arteries in SIV-HIV-Nef-infected macaques, which showed a relatively high percentage of blood cells constantly probing vascular endothelial cells [69], Thus, endothelial cells, especially those in developing atherosclerotic plaques, are constantly in direct contact with circulating monocytes and T cells and in prime physical position to receive Nef transfer. In the proinflammatory conditions associated with viremic and even aviremic HIV infection, endothelial cell activation leads to increased vascular adhesion protein and chemokine expression.…”

“…In fact, transgenic mice expressing CD4-promoter-driven Nef develop a spectrum of pathologies including AIDS-like disease [64] and vasospasm in the heart [65], and certain Nef gene variants were linked to pulmonary hypertension [66, 67]. We have recently reported that HIV-infected T cells are more potent than free virus in activating coronary arterial endothelial cells [68]. There is evidence that this effect is Nef-dependent.…”

Vascular endothelial dysfunction in the wake of HIV and ART

“…Tat Gp120 ↑ROS e [29] ↑oxidative stress h [28] ↑VCAM-1 e [29] ↑ICAM-1 a [30] ↓claudin-1 h [31] ↓claudin-5 h [31] ↓ZO-2 h [31] ↓occludin f [32] ↑apoptosis g [35] ↑oxidative stress h [28] ↓eNOS d [38] Nef Vpu Vpr ↑ROS d,e,i [41,42] ↑oxidative stress e,i [42] ↓eNOS e,i [42] ↑MCP-1 d [41] ↑apoptosis d [41] ↑VCAM-1 a [46] ↑apoptosis f [47] Proinflammatory cytokines TNF-a IL-6/CRP IL-1b ↑ROS a [61] ↓eNOS d [38] ↑ICAM-1 d,f [38,63] ↑ICAM-1 f [63] ↓eNOS a,b,c [80,81] ↓NO a,b,c [80,81] ↑ICAM-1 a,d [79] ↑VCAM-1 a,d [79] D ZO-1 a [82,83] D VE-cadherin a [83] ↑ICAM-1 a,f [63,70] ↑VCAM…”

Inflammation, immune activation, and cardiovascular disease in HIV

“…In vitro studies have shown the following proatherogenic effects of HIV viral proteins: A) Tat and gp120 induces expression of adhesion molecules [179, 180]; B) Nef and gp120 reduce endothelial NO production [181, 182]; C) Nef increases inflammatory cytokine release including IL-6 and TNF-alpha from macrophages [183]; D) Nef promotes MCP-1 secretion from endothelial cells [184]; E) Tat stimulates MCP-1 mediated monocyte transmigration [185]; F) Nef inhibits ABCA1-dependent CEC of macrophages [76]; G) Nef and gp120 may induce endothelial apoptosis, which could promote fibroatheroma rupture/erosion, resulting in formation of an acute thrombus [186, 187]; H) Tat stimulates IL-6 production from peripheral blood monocytes [188]. In vitro studies have also shown potential proatherogenic effects of specific ARTs including increased leukocyte adhesion to endothelial cells with efavirenz [189]; increased platelet reactivity with abacavir [190]; reduced cholesterol efflux from macrophages, decreased endothelial nitric oxide production, and endothelial cytotoxicity with ritonavir [191–193]; and CD36-dependent cholesterol accumulation in macrophages with certain protease inhibitors [194].…”